1. Field of the Invention
This invention relates to drilling muds and, more particularly, to a novel process for removing hydrocarbon contaminants from used drilling mud.
2. The Prior Art
Hydrocarbons such as crude oil and natural gas are recovered from wells or boreholes drilled deep into the earth. Conventionally, the borehole is drilled using a rotary drill bit on the end of a rotatable, hollow drill stem. A drilling fluid is pumped downwardly through the hollow drill stem to cool and lubricate the drill bit while at the same time carrying the cuttings upwardly through the annular space surrounding the drill stem. The drilling fluid and the cuttings are circulated to the surface where the cuttings are removed so that the drilling fluid can be recycled into the system. Customarily, water is the primary ingredient of this drilling fluid along with specific types of clays and other additives which are included to create a drilling fluid having preselected characteristics to meet the requirements of the particular formation being drilled. Due to the presence of clay in the drilling fluid, the drilling fluid is commonly referred to as "drilling mud" or simply as "mud."
Clearly, the term "mud" is too simplistic to give one a true picture of the significant body of science that has evolved over the past century in the field of drilling fluids. Numerous advances have been made in the formulations for drilling muds to be used under various applications. Clay, of course, is the major ingredient and is usually selected from clays such as bentonite, attapulgite, and sepiolite, to name a few. Various additives are blended into the drilling fluid to develop viscosity, control fluid loss, reduce corrosion, control the rheological properties under extreme conditions of temperature and contamination, and act as a filtration control agent, for example.
Ultimately, the borehole is drilled to its preselected depth through the desired hydrocarbon-producing formation. During this phase of the drilling operation significant quantities of hydrocarbons from the formation become incorporated with the drilling mud, which means that the drilling mud becomes contaminated with hydrocarbons thereby creating a hazardous waste problem. This problem is particularly exacerbated by the nature of the drilling mud in the first place, namely, that great care is taken to assure that the clay material remains suspended in the drilling fluid and thereby does not plug the producing formation. This fact and the presence of hydrocarbons means that the cleanup of contaminated drilling mud presents a particularly troublesome cleanup problem.
In view of the foregoing, it would be an advancement in the art to provide a process for removing hydrocarbons from drilling mud residues. It would be an especially significant advancement in the art to provide a process for not only separating hydrocarbon residues from a drilling mud residue but also to separate a relatively clean water from the drilling mud. Such a novel process is disclosed and claimed herein.